Quantum-state–selective electron recombination studies suggest enhanced abundance of primordial HeH +

Abstract

Enhanced abundance of primordial HeH + Though only recently detected in space, the helium hydride ion (HeH + ) is thought to be the first molecule ever to have formed in the early Universe. Novotný et al. report state-specific rate coefficients for the dissociative reaction of HeH + with electrons, obtained using a cryogenic ion storage ring combined with a merged electron beam (see the Perspective by Bovino and Galli). They detect substantial rotational dependence and a decrease of the rates for the lowest states of HeH + , far below the values listed in astrochemistry databases and those previously applied in early-Universe models. These results suggest high abundance of this important primordial molecule at redshifts of first star and galaxy formation. Science , this issue p. 676 ; see also p. 639